Lock-out, tag-out system using safety programmable logic controller

1. A lock-out, tag-out system for a power control cabinet, the lock-out, tag-out system comprising: (1) at least one lock-out, tag-out station providing: (a) contacts having a shared operator for receiving a padlock when the operator is in a deactivation position, the padlock blocking actuation of the operator, (b) a display indicating deactivation of at least one associated motor circuit; and (c) a station safety network interface element communicating with the contacts and display to transmit a contact state and receive a display state using redundant communication on a serial network; (2) a safety programmable logic controller communicating with the serial network the safety programmable logic controller executing a stored program to receive the contact state and the display state and to redirect them on the serial network according to a stored program; (3) at least one power control circuit positionable in the power control cabinet, the power control circuit providing: (a) a first and second contactor each providing a coil switching independent contacts, the contacts of the first contactor in series with contacts of the second contactor to communicate, when closed, electrical power between a power source and motor circuitry; (b) a voltage sensor detecting voltage at a connection between the motor circuitry and the first and second contactor to detect removal of power from the motor circuitry; (c) a cabinet safety network interface element communicating on the serial network to receive the contact state to control the coils of the first and second contactors and transmit display state derived from the voltage sensor detecting removal of power from the motor circuitry.

2. The lock-out, tag-out system of claim 1 wherein at least one of the station and cabinet safety network interface elements is an I/O module of the safety PLC providing communication between the PLC and the I/O module using redundant communication on a serial network.

3. The lock-out, tag-out system of claim 1 wherein the power control circuit further includes a third contactor having a coil, the contacts of the third contactor connecting between isolated ground and the connection between the motor circuitry and the first and second contactor, wherein the cabinet safety interface element receives the contact state to control the coil of the third contactor to ground the motor circuitry when contacts of the first and second contactor are open.

4. The lock-out, tag-out system of claim 1 wherein the serial network provides a probability of failure on demand of 0.001-0.0001.

5. The lock-out, tag-out system of claim 1 wherein the station safety network interface element transmits a contact state causing an opening of the contacts of the first and second contractor when one or both of the contacts of the operator are open.

6. The lock-out, tag-out system of claim 1 wherein the power control circuit is in a housing meeting IEEE C 37.20.7-2007 standards for are suppression.

7. The lock-out, tag-out system of claim 1 further including a bucket of a motor control center haying an enclosure providing for multiple buckets holding circuitry communicating with motor circuitry; wherein the power control circuit is attached within the bucket.

8. The lock-out, tag-out system of claim 1 wherein the power control circuit further includes a device selected from the group consisting of: a contactor, a motor starter, a solid-state starter and a motor drive between the second contacts and the motor circuitry.

9. The lock-out, tag-out system of claim 1 wherein the stored program of the programmable logic controller redirects contact state from different lock-out, tag-out stations to a single second safety network interface and redirects display state from the single safety network interface to the different lock-out tag out stations; wherein the display associated with each lock-out, tag-out station only indicates the deactivation for individual lock-out, tag-out stations whose operators are in the deactivation position.

10. The lock-out, tag-out system of claim 1 wherein the stored program of the programmable logic controller redirects contact state from a single lock-out, tag-out station to at least two second safety network interfaces and redirects the display state from at least two safety network interfaces to a single lock-out, tag out station associated with multiple power control circuits; wherein the display indicates deactivation only when removal of power has occurred at all of multiple remote locations associated with the multiple power control circuits.

11. The lock-out, tag-out system of claim 1 further including a second standard programmable logic controller communicating with the serial network, the second programmable logic controller executing a stored program to receive and transmit data from and to a standard I/O module adapted for communication with an industrial process.

12. A power control circuit for a power control cabinet comprising an arc-flash resistant housing and holding: a first and a second contactor each providing a coil switching independent contacts, the contacts of the first contactor in series with contacts of the second contactor, each series-connected contact receiving at a first terminal electrical power from the second releasable electrical connector from a power source and providing switched power from a second terminal to the second releasable electrical connector for operation of a motor; a voltage sensor detecting voltage at the second terminal; a safety network interface element providing control signals to the coils of the first and second contactors and communicating with the voltage sensor to receive input signals from the voltage sensor, the safety network interface element providing redundant communication on a serial network with remote lock-out switches to receive data of the control signals and to transmit data of the input signals on the serial network.

13. The power control circuit of claim 12 wherein the power control circuit further includes a third contactor having a coil and communicating between the contacts of the third contactor connecting between isolated ground and the connection between the motor circuitry and the first and second contactor, wherein a second safety interface element receives the contact state to control the coil of the third contactor to ground the motor circuitry when contacts of the first and second contactor are open.

14. The power control circuit of claim 12 wherein the power control circuit further includes at least one of a device selected from the group consisting of: a contactor, a motor starter, a solid-state starter and a motor drive between the second contacts and the motor circuitry.

15. A lock-out, tag-out system for a motor control center of the type providing for multiple bucket-receiving openings and holding conductors for communicating with motor circuitry, the lock-out, tag-out system providing a bucket comprising an arc-flash resistant housing fitting within the motor control center and holding: a first contactor providing a coil switching contacts receiving at first terminals electrical power from a power source and providing switched power at second terminals; a voltage sensor detecting voltage at the second terminals; a safe-off motor drive having power terminals connected to the second terminals, the power terminals providing internal power for the safe-off motor drive, the safe-off motor drive further including a switch element disconnecting internal power from power semiconductors used to synthesize motor drive voltages; a safety network interface element: (a) providing a control signal to the coil of the first contactor; (b) communicating with the voltage sensor to receive input signals from the voltage sensor; (c) providing, a control signal to the switch element; the safety network interface element providing redundant communication on a serial network with remote lock-out switches to receive data of the control signals and to transmit data of the input signals on the serial network.

16. The lock-out, tag-out system of claim 15 further including a lock-out, tag-out station comprising: (a) contacts having a shared operator, the operator adapted to receive a padlock when the operator is in a deactivation position, the padlock blocking actuation of the operator, (b) a display indicating deactivation of at least one associated motor circuit; and (c) a second safety network interface element connected to the contacts and the display to transmit a contact state and receive a display state using redundant data on the serial network configured to provide communication to at least one bucket of a motor control center.

17. The lock-out, tag-out system of claim 15 further including a safety programmable logic controller communicating with the serial network, the safety programmable logic controller executing a stored program to receive the contact state and the display state and to redirect them on the serial network according to a stored program.